The compound prepared by the process of this invention is a known compound disclosed in U.S. Pat. No. 4,587,247. The compound can be prepared through an ardous chemical epimerization, and has also been prepared microbiologically as described in U.S. Pat. No. 4,666,937. The instant process offers a novel preparation of the 13-.beta. compound directly from the natural product 13-.alpha.- compound using any one of three microorganisms, two of which are novel.